Control of reversible vibratory equipment

ABSTRACT

A resiliently supported vibratory conveyor or processing unit is equipped with a plurality of tunable dynamic vibration absorbers and controls so that the vibratory response of the unit to the centrifugal force of rotating eccentric weights journalled in the unit may be varied from a minimum to a maximum amplitude along either of a pair of oppositely inclined paths of movement.

United States Patent [1 1 Schrader 1 1 CONTROL OF REVERSIBLE VIBRATORY EQUIPMENT [75] Inventor: Preston Henry Schrader,

Middletown, Ky.

[73] Assignee: Rexnord Inc., Milwaukee, Wis.

[22] Filed: July 2, 1973 [21] Appl. No.: 375,786

Related U.S. Application Data [63] Continuation-impart of Ser. No. 200,892. Nov. 22,

[52] US. Cl 198/220 CC; 198/220 DB; 209/367 51 lm. Cl. B65g 27/00 [58] Field of Search 198/220 CC, 220 DD, 198/220 DB; 209/3665, 367, 326,

[56] References Cited UNITED STATES PATENTS 3,068,996 12/1962 Musschout 198/220 CC [451 July 1, 1975 3,253,701 5/1966 Evans 209/367 X Primary ExaminerEvon C. Blunk Assistant Examiner-Douglas D. Watts Attorney, Agent, or FirmMarshall 8L Yeasting [5 7] ABSTRACT A resiliently supported vibratory conveyor or processing unit is equipped with a plurality of tunable dynamic vibration absorbers and controls so that the vibratory response of the unit to the centrifugal force of rotating eccentric weights joumalled in the unit may be varied from a minimum to a maximum amplitude along either of a pair of oppositely inclined paths of movement.

4 Claims, 2 Drawing Figures x rn SHEET AMPLITUDE 0F VIBRATION OF MEMBERS IO PRESSURE AMPLITUDE OF VIBRATION OF TQOUGH 1 CONTROL OF REVERSIBLE VIBRATORY EQUIPMENT RELATED APPLICATIONS This application is a continuation-in-part of applica tion Ser. No. 200,892, filed Nov. 22, 1971.

SUMMARY OF THE INVENTION According to the invention, a resiliently mounted conveyor or processing unit driven by rotating eccentric weights is provided with at least two sets of tunable dynamic vibration absorbers that may be selectively tuned to either oppose or aid the eccentric weights in producing vibration of the conveyor or unit along either of a pair of axes. A processing unit operating according to the invention is illustrated in the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a schematic side elevation of a processing unit and the controls for tuning the absorbers.

FIG. 2 is a graph showing the relationship between the inflation pressure and the amplitudes of vibration of the work member and absorber members.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT A vibratory conveyor or processing unit that may be vibrated to convey material in either direction to either discharge material or level the material in the unit may comprise a container or trough constituting a work member 1 that is elastically supported for vibration on a plurality of vibration isolators in the form of air springs 2. The work member is vibrated by eccentric weights 3 mounted on a shaft 4 journalled in the work member 1. The shaft 4 may be the rotor shaft of a motor for direct drive or it may be belt driven from a motor 5 mounted on the work member. The shaft 4 is located near the center of gravity of the work member. Without absorbers, to be described, the work member would vibrate in a generally circular orbit in response to the centrifugal force of the eccentric weights 3.

The direction and amplitude of vibration of the work member I in response to the centrifugal force of the eccentric weights 3 is controlled by a plurality of tunable dynamic vibration absorbers 6, 7, 8 and 9. Each of the absorbers comprise a mass of vibrating weight 10 that is guided with respect to the work member by rocker arms 11 connected between the weight and work memher I. The motion of the weight 10 is controlled by a pair of air springs 12, the spring rate of which may be adjusted by adjustment of the inflation pressure of the air springs. As shown, the air springs 12 are arranged on opposite sides of the weight 10 so that the springs oppose each other insofar as static pressures and forces are concerned. During vibration, as one spring expands the other is compressed so the effective spring rate of the pair urging the weight I0 to the center of its path of movement is the sum of the individual spring rates.

According to the preferred method of operation the absorbers are arranged in pairs, the members of each pair being generally equidistant from the center of gravity of the work member 1. The absorbers 6 and 9 form one pair adapted to vibrate along a path inclined upwardly toward the left. The absorbers 7 and 8 form a second pair adapted to vibrate along a path inclined upwardly toward the right.

If one pair of absorbers, such as the pair 6 and 9, are tuned so that the weights 10 in combination with the springs 12 are resonant at the operating speed of the eccentric weights, the weights vibrate at such amplitude and phase as to practically counterbalance the force of the eccentric weights in the direction of vibration of the weights. Thus, there is little or no vibration of the work member in that direction.

If at the same time the other pair of absorbers 7 and 8, are tuned so that work member 1 as one member and the weights 10 of the absorbers 7 and 8 as the other member and the cooperating air springs form a two mass vibratory system that is resonant near the operating speed, preferably just below the operating speed. With this tuning the weights 10 of the absorbers 7 and 8 vibrate in phase with the eccentric weights 3 to reinforce or augment the force of the eccentric weights to increase the vibration of the work member along the path of vibration of the weights 10 of the absorbers 7 and 8. By varying the tuning the amount of reinforcement of the force may be varied to vary the amplitude of vibration of the work member.

The relation between the amplitude and phase of vibration of the work member and absorber weights with relation to the eccentric weights is shown in the graph, FIG. 2. When the inflation pressure is low, at the left in the figure, the resonant frequency is low, the work member I vibrates at an amplitude X1 while the weights l0 vibrate at an amplitude X2. At a pressure Pl the amplitude of vibration XI of the work member is about twice that obtained without any absorbers. As the pressure is increased the amplitudes of vibration increase to a maximum determined by the damping in the springs 12. A further increase in pressure raises the natural frequency until at a pressure P2 the amplitude of vibration of the work member I becomes practically zero.

Since the absorbers 6, 7, 8, and 9 are arranged in pairs acting along different paths, it is possible to select both the direction of vibration (direction of vibratory conveying) and the amplitude of vibration by inflating the several air springs to the proper pressures. Although a working amplitude of vibration may be obtained with inflation pressures above or below the pressure Pr for resonance, one must tune much closer to resonance when operating on the high pressure side of resonance. Thus, for stability it is desirable to operate at the lower pressures when vibrating the work member 1.

Since the pressure P2 for vibration suppression and the preferred pressure PI for increased or working amplitude of vibration are separated by the pressure Pr at resonance, and since the system may be self destructive at resonance one cannot reverse the direction of vibration while the eccentric weights are rotating at full speed. Furthermore, since at the desired operating pressure Pl, the operating frequency is just above the resonant frequency of the system, it is practically impossible to accelerate the eccentric weights through the resonant frequency. Therefore, in a practical system it is necessary to inflate the air springs of those absorbers that are to suppress vibration of the work member 1 to the pressure P2 while reducing the pressure in the other air springs to a pressure much lower than the working pressure P1 before starting the motor 5. Once the motor 5 is running and the eccentric weights 3 are rotating at the operating frequency the low pressure air springs may be inflated to the working pressure P1.

The control equipment to properly inflate the air springs for vibratory conveying in either direction is illustrated in the lower part of FIG. 1. As shown this equipment comprises a connecting 20 to a source of compressed air, a primary pressure regulator 21 pressure gage 22 and filter 23 to supply clean air under pressure to an air supply manifold 24.

From the air supply manifold 24, air is supplied through pressure regulators, needle valves and three way valves to the air springs of the several absorbers 6, 7, 8 and 9. To set the equipment, for example, to convey to the right, the air pressure in the air springs of absorbers 6 and 9 is set at pressure P2 while the pressure in absorbers 7 and 8 is set near pressure Pl. Thus, the supply line 24 is connected through pressure regulator 25 (set to pressure P2) and needle valve 26 to pressure line 27 and through three way reversing valves 28 and 29 and lines 30 and 31 to the springs of absorbers 6 and 9.

At the same time absorbers 7 and 8 are pressurized through lines 32 and 33 respectively connected through reversing valves 34 and 35, and start up valves 36, 37 to lines 38, 39 controlled by pressure regulators 40, 41 and needle valves 42, 43. All of the needle valves are supplied to control the rate at which the pressures may be changed. The pressure regulators 40 and 41 set the pressures in the absorbers 7 and 8 at pressure Pl (FIG. 2) to control the amplitudes of vibration. Individual regulators are used to permit fine adjustment of the tuning to compensate for variations in the air springs and other components of the system. During the run condition solenoid valve 44 is energized so that line pressure from line 24 is applied through valve 44 to the actuators of start up valves 36, 37, 45 and 46 and these valves connect lines 38 and 39 to the reversing valves. During start up, before solenoid valve 44 is energized, the valves 36, 37, 45, and 46 are in the positions shown so that a low pressure controlled by pressure regulator 47 is applied to the air springs of absorbers 7 and 8. Pressure switches 48, 49, 50 are connected to each of the controlled pressure lines and included in the electrical start and run controls of the motor to prevent starting and to stop the motor in the event improper pressures exist in the related lines.

When the system is de-energized the air springs of absorbers 7 and 8 are connected to regulator 47 and are at low pressure to close contacts of switch 48 to allow the motor to start the remaining switches 49, 50, are in the hold circuit of the motor starter to de-energize the motor if the pressures Pl become too high or the pressure P2 in line 27 becomes too small.

If the direction of conveying is to be reversed, solenoid operated valve 51 is energized to supply pressure to the operators of the reverse valves 28, 29, 34, and 35. This has the effect of applying pressure P2 from line 27 to the air springs of absorbers 7 and 8 while connecting lines 30 and 31 of absorbers 6 and 9 through start up valves 45 and 46 to lines 52, 53 controlled by pressure regulators 54, 55. The operation for the reverse direction of conveying is then as previously described for operation in the forward direction of conveying.

Since damage could result from deflation of the air springs 2 used as vibration isolators supporting the work member 1, these isolators are inflated through a line 56 controlled by a pressure regulator 57 and monitored by a pressure switch 58 arranged to stop the motor 5 in the event of loss of inflation pressure,

The arrangement of the various sets of absorbers on a work member subjected to centrifugal force of rotating eccentric weights allows the direction and amplitude of vibration to be readily selected and controlled by variation in air pressure in the springs of the absrohers.

I claim:

1. A method of controlling the vibration of an elastically supported work member in response to vibratory force of rotating eccentric weights journalled in the member and equipped with tunable dynamic absorbers arranged in sets each operative along a particular path that comprises, tuning a first set of said absorbers to oppose motion of said work member along a first path and simultaneously tuning a second set of said absorbers to form a two mass vibratory system to control the amplitude of the vibratory motion of said work member along a second path.

2. A method of control according to claim 1 in which each of said absorbers includes air springs the inflation pressure of which is varied to tune the absorber.

3. A method according to claim 1 in which the first and second paths are approximately at right angles to each other.

4. A method according to claim 1 in which the natural frequency of the two mass vibratory system is near the operating speed of the rotating eccentric weight. 

1. A method of controlling the vibration of an elastically supported work member in response to vibratory force of rotating eccentric weights journalled in the member and equipped with tunable dynamic absorbers arranged in sets each operative along a particular path that comprises, tuning a first set of said absorbers to oppose motion of said work member along a first path and simultaneously tuning a second set of said absorbers to form a two mass vibratory system to control the amplitude of the vibratory motion of said work member along a second path.
 2. A method of control according to claim 1 in which each of said absorbers includes air springs the inflation pressure of which is varied to tune the absorber.
 3. A method according to claim 1 in which the first and second paths are approximately at right angles to each other.
 4. A method according to claim 1 in which the natural frequency of the two mass vibratory system is near the operating speed of the rotating eccentric weight. 